1. Field of the Invention
The present invention relates to a forming machine executing an injection molding of a polymeric material such as a rubber, a resin and the like.
2. Description of the Related Art
As an injection molding machine of a rubber for injecting a rubber to a resin product after being molded so as to mold a packing, a rubber wire or the like which is integrally molded with the resin product, there has been conventionally known a structure which is provided with a rubber injecting apparatus, a turntable and a mold mounted on the turntable. In this injection molding machine, the structure is made such that the mold moves between a position below an injection nozzle of the injection apparatus and a position for attaching and detaching the resin product together with a rotation of the turntable. The mold is constituted by one upper portion executing a vertical motion at a position below the injection nozzle so as to clamp and open the mold, and two lower portions fixed to the turntable.
In order to molding by using the injection molding machine, the resin product is set to the lower dies at the attaching and detaching position, the upper die is clamped at the position below the injection nozzle by rotating the turntable, and thereafter the rubber is injected. At a time of injection, the rubber is vulcanized by pressing the injection nozzle of the injection apparatus to a nozzle touch portion in the upper portion, injecting the rubber within a cavity of the mold and further mainly overheating the lower dies.
As another injection molding machine, there is a structure disclosed in Japanese Patent Application Laid-Open No. 7-223235 in which more stations are provided than those in the injection molding machine mentioned above. In this molding machine, a thermosetting resin is injected, cured and taken out from the mold during a period that a mold apparatus moves among the respective stations by a rotary apparatus.
Further, there has been known a rotary injection molding machine in which a dwell pressure application apparatus is mounted to each of a plurality of molds arranged in the turntable. In this molding machine, the mold is opened and closed by an opening and closing hydraulic cylinder provided within a machine table at a mold detaching position, and the mold is clamped by a hydraulic cylinder provided within a machine table at an injecting position. A fluid flowing out to a circuit from the hydraulic cylinder for dwell pressure application in correspondence to the opening and closing operation of the mold is recovered by an accumulator so as to be reused.
In the rubber injection molding machine mentioned above, it is necessary to keep a state of pressing the injection nozzle to the nozzle touch portion in the upper portion until the rubber is completely vulcanized. Because the rubber within the cavity flows backward from the nozzle touch portion due to an internal pressure so as to be discharged out of the mold if the injection nozzle is detached away from the nozzle touch portion before the rubber is completely vulcanized. Accordingly, one cycle operation for molding the rubber is constituted by setting resin product to the lower portion, rotating the turntable, clamping the upper portion, injecting the rubber, vulcanizing, rotating the turntable and opening the mold which are executed sequentially, and accordingly, a long time is required. Therefore, in the conventional rubber injection molding machine, a rubber curing time gives an influence to a production efficiency.
In the molding machine disclosed in Japanese Patent Application Laid-Open No. 7-223235, it is unavoidable that the resin flows backward from the portion at which the resin material is injected to the mold apparatus from the injection nozzle so as to be discharged. Accordingly, there has been generated a problem that an accuracy of the molded product is reduced, and a burr is formed in the product. Further, it is necessary to reduce an amount of the resin injected to the mold apparatus in a side of the injection apparatus so as to supply, so that in the case of producing the products having different standard specifications by the same apparatus, a special control is required with respect to the injection apparatus. Accordingly, in this conventional apparatus, it is hard to mold plural kinds of products by one molding apparatus.
Further, in the rotary injection molding machine to which the dwell pressure application apparatus is mounted, there have been problems such that the load of the dwell pressure application apparatus is great with respect to the turntable, the apparatus for opening and closing or clamping the mold via the dwell pressure application apparatus is required, whereby the structure becomes complex and it is hard to make the structure compact and light, and the opening and closing speed is restricted in correspondence to the recovery and reuse of the fluid flowing out into the circuit.
An object of the present invention is to provide a molding machine which can significantly improve a production efficiency and can easily mold plural kinds of products. Further, another object of the present invention is to provide a molding machine which can individually and safely execute an opening and closing operation of a mold and a mold clamp in accordance with a simple structure by employing an air operation in place of a fluid pressure.
A first aspect of the present invention provides a molding machine comprising: a turntable having a driving gear; a plurality of molds placed along a peripheral edge of the turntable; an injection portion for injecting a molding material; the mold being sequentially moved to a position at which the injection portion is arranged, by driving the turntable; and an injection nozzle of the injection portion being communicated with a material receiving port of the mold so as to inject the molding material within the mold, wherein the molding machine comprises: a setting and detaching station setting a primary formed product previously molded in the mold and detaching a secondary formed product secondarily molded from the mold; an injection station applying a secondary mold to the primary formed product set to the mold in the set and detaching station; and a curing station arranged between the injection station and sat and detaching station and curing the molded material secondarily molded, and wherein the mold is provided with a back-flow preventing mechanism for closing the material receiving port.
In the structure mentioned above, since there is provided the back-flow preventing mechanism for closing the material receiving port in the mold, the back-flow preventing mechanism closes the material receiving port even when the injection nozzle is moved away from the material receiving port after the molding material is injected within the material receiving port from the injection nozzle in the injection portion, so that the molding material does not flow backward from the mold and it is possible to reduce a time for an injecting step. Since it is possible to individually execute the injecting step in the injection station, a curing step in the curing station and a setting and detaching step in the set and detaching station in each of the stations in the manner mentioned above, it is possible to independently arranged the respective steps in view of a position without being affected by a state of the molding material in the material receiving port, and it is possible to execute an injection process in a fast manner.
Accordingly, it is possible to improve a production efficiency of the molded product. Further, due to the back-flow preventing mechanism, it is possible to mold at a high accuracy without reducing a pressure of the molding material within the mold.
Further, a second aspect of the present invention provides a molding machine according to the structure mentioned above, wherein the mold is constructed by a combination of an upper portion and a lower portion, a material flow channel communicating with the material receiving port is formed in the upper portion along a vertical direction, and a back-flow preventing rod is fitted within the material flow channel so as to freely move in a vertical direction. The back-flow preventing rod is always urged upward, and closes the material receiving port in a state that an upper end protrudes out from the material receiving port, and when the injection nozzle moves downward so as to press down the upper end of the back-flow preventing rod, the molding material can be injected within the material flow channel. It is possible to prevent the molding material from backward flowing from the mold with requiring no complex mechanism.
Further, a third aspect of the present invention provides a molding machine according to the structure mentioned above, wherein a molding cavity is formed in a portion in which the upper portion and the lower portion are bonded. A primary formed product which has been already molded is arranged within the molding cavity, and a secondary forming is applied to the primary formed product by adding the molding material. In accordance with the structure mentioned above, in addition to the operation in the structure mentioned above, it is possible to easily and effectively execute an insert molding be previously arranging the primary formed product within the molding cavity.
A fourth aspect of the present invention provides a molding machine according to the structure mentioned above, wherein a material intake channel communicating with the material flow channel is formed in the upper portion, and a piston mechanism opening and closing the material pouring port through which the molding material is pouring into the mold is provided in the upper portion. In accordance with the piston mechanism, it is possible to open and close the material pouring.
A fifth aspect of the present invention provides a molding machine according to the structure mentioned above, wherein the molding material is a thermosetting resin, and a curing process of the molding material is performed by a heating apparatus. It is possible to effectively perform an injection molding with the thermosetting resin such as a rubber or the like, and it is possible to securely control a curing step.
A sixth aspect of the present invention provides a molding machine according to the structure mentioned above, wherein the injection portion is operated due to a hydraulic pressure, a mold clamping apparatus driven by pneumatic circuit is placed on the turntable together with the mold, and the mold clamping apparatus clamps the upper portion and the lower portion. Since the mold is opened and closed or clamped due to an air operation, it is possible to securely execute the mold clamping and the dwell pressure application by a simple structure.
A seventh aspect of the present invention provides a molding machine according to the structure mentioned above, wherein the mold is constructed by a combination of an upper portion and a lower portion, a material flow channel communicating with the material receiving port is formed in the upper portion along a vertical direction, a heating apparatus for heating the material flow channel is provided, a thermosetting molding material applies a secondary forming to a primary formed product from the material receiving port, and the heating apparatus cures the molding material within the material flow channel so as to close the material receiving port.
The molding material is injected from the injection nozzle of the injection portion to the material receiving port so as to apply the secondary forming to the primary formed product within the mold, and the molding material is cured within the material flow channel heated by the heating apparatus. Accordingly, it is possible to close the material receiving port by the molding material curing within the material flow channel so as to prevent the molding material from backward flowing from the mold.